Ultraviolet ray and sun-proof _ moisten skin

Ultraviolet ray and sun-proof _ moisten skin
Scorching Xia Ri, the skin regards the situation as very grave or critical, how to prevent suntan and whiten and become topics that people care about naturally. As to the thing that " how the ultraviolet ray injures the skin, the cloudy day needs to prevent suntan, how to choose the sun-proof product" Waiting a moment, you may have a series of doubt. And these questions, you can find the answer in the following contents.

How much does ultraviolet ray know

The ultraviolet ray can be divided into long wave UVA, mediumwave UVB and shortwave UVC three kinds according to the wavelength. The longer the wavelength is, it is the stronger to penetrate ability.

UVA causes the skin to damage and wear out


Long wave UVA, the wavelength lies between 320- 400 nanometers, have very strong penetrating strength, can penetrate the glass, even 9 feet of water; And throughout the year, no matter all exist overcastly and finely and daily. Above 95% of ultraviolet ray that the daily skin touches is UVA, so its injury to the skin is the greatest. UVA can attack the dermis floor through the epidermis, makes bone collagen and elastin in the skin mauled; And dermis cell self-protection ability is relatively bad, very small UVA can cause the great injury. As time passes, the question of appearing etc. that the skin produces limp, wrinkles, blood capillary. Meanwhile, it can activate enzyme hydroxyphenylaminopropionic acid, causes melanin depositing and new melanin immediately to take shape, make the skin darken, lack the gloss. UVA will cause long-term, chronic and lasting damage, makes the skin old and feeble too early, known as the aging ray again.

UVB causes the skin to sunburn immediately


Mediumwave UVB, the wavelength lies between 290- 320 nanometers, will make the lipid layer with protective action of epidermis oxidize, make the skin become dry; Further make nuclear acid and albumen quality in epidermis cells change the sex, produce acute dermatitis (sunburn) Wait for symptom, the skin will turn red, sore. When being serious, for example tanning by the sun for a long time, it is apt to cause the skin canceration. In addition, the long-term injury of UVB will also cause black and chromatophorous variation, causes the sun spot different to dispel.

U V C no the skin of influence is healthy


Shortwave UVC, the wavelength lies between 200- 290 nanometers, has been absorbed by the ozone layer before reaching the ground, so its impact on skin can be neglected.

The literature of science and clinical trial indicates, the skin damage that UVB causes is instant and serious, UVA damage to the skin is chronic for a long time. So ideal the intersection of shelter and product should security high less irritating, possess, resist UVA and function of UVB at the same time while being key.

S P F resists U V B

SPF(Sun Protection Factor) ,Everybody familiar with, follow closely following number value known as sun-proof coefficient or sun-proof multiple far and wide, used for assessing the result that the sun-proof products resist UVB. The level of SPF value is from reflecting the size to the ultraviolet UVB protective capacity of the sun-proof products objectively. While determining SPF value, daubs the sun-proof product on selected a piece of skin, skin of another one does not apply any product. Then shine until two pieces of skin erythema appears separately with UVB, and record different time of shining of ultraviolet ray under two kinds of conditions, its ratio is SPF value of this sun-proof product.

SPF value calculates formulae

SPF =Daub MED MED * not daubing the skin of sun-proof product of the skin of sun-proof product

*MED( Minimal Erythema Dose) Minimum erythematous quantity, guide and get up and can be seen erythema (suffused with red) most slightly The necessary lowest dosage (J/m2) of ultraviolet ray Or the shortest time of shining.

Can find out the bigger SPF value is, the stronger the ability to resist UVB is. One SPF 15 sun-proof products in value, can interpreted as, be able to make skin resist and shine red, that the ability to resist UVB has been improved by 15 times.

P A resists U V A


Protect the appraisal of the result, still none of more unified determination methods in the world at present on UVA. The determination method that some countries consult SPF value is used " The human spot sticks to the experiment " Determine PFA (Protection Factor of UVA) The value, then convert to PA hierarchical method to express the shelter result to UVA of the sun-proof product. Examine and use UVA light source regularly, shine the skin until presenting black melting or pigmentation separately, record and compare with time.

PFA value calculates formulae

PFA =It is worth * to daub MPPD value MPPD not daubing the skin of sun-proof product of the skin of sun-proof product

*MPPD( Minimal Persistent Pigmentation Dose) ,Black to melt or pigmented quantity. Guide and get up and can be seen the lowest dosage (J/m2) of ultraviolet ray that black melting or pigmented quantity needs Or the shortest time of shining.

Similar to definition of SPF, one PFA 5 sun-proof products in value, can interpreted as, be able to make skin resist tanned, that the ability to resist UVA is improved by 5 times.

But usually, the sun-proof coefficient of resisting UVA will show with PA, this is a hierarchical formula expression method. PFA value that it will determine is converted to PA according to certain corresponding relation. Follow + number closely behind PA, + the more number is, the stronger the representative's ability to resist UVA is.



|